In a report following an 18-month probe of the flawed gun-smuggling investigation, Rep. Darrell Issa of California and Sen. Chuck Grassley of Iowa said that the administration shifted the emphasis in fighting Mexican drug cartels from merely seizing firearms to identifying the networks that traffic them.

Operation Fast and Furious "was born from this strategy," the report concluded.

In Operation Fast and Furious and at least three earlier probes during the administration of Republican President George W. Bush, agents in Arizona employed a risky tactic called gun-walking - allowing low-level "straw" buyers in gun-trafficking networks to leave with loads of weapons purchased at gun shops. The goal of the tactic was to track the guns to major weapons traffickers and drug cartels in order to bring cases against kingpins who had long eluded prosecution under the prevailing strategy of arresting most low-level purchasers of guns who were suspected of buying them for others.

In Operation Fast and Furious, many of the weapons weren't tracked and wound up at crime scenes in Mexico and the U.S., including at the site of a shootout on the U.S. side of the border that resulted in the death of a border agent, Brian Terry. Fast and Furious identified more than 2,000 weapons suspected of being illicitly purchased. Some 1,400 of them have yet to be recovered.

Justice Department spokeswoman Tracy Schmaler said that the Republican report "reiterates many of the distortions and now-debunked conspiracy theories that Rep. Issa has been advancing for a year and a half, including the fiction that the flawed tactics used in Fast and Furious were somehow the brainchild of the current administration as opposed to the reality that the pattern of flawed tactics dates back to 2006 and the prior administration."

The gun-walking tactic that Issa and Grassley are linking to the Obama administration has long been against Justice Department policy.

The Justice Department did adopt a strategy in 2009 for fighting Mexican cartels that said merely seizing firearms through interdiction would not stop firearms trafficking to Mexico. And records show that more than 68,000 guns reached Mexico from the U.S. over the last five years despite the long-standing policy of arresting low-level participants in suspected gun-running. "We must identify, investigate, and eliminate the sources of illegally trafficked firearms and the networks that transport them," the department stated.

Issa's report says that federal agents and William Newell, head of the Phoenix division of the Bureau of Alcohol, Tobacco, Firearms and Explosives, may have viewed the Justice Department strategy statement as "the green light they had been waiting for" to engage in what became Operation Fast and Furious.

The report says that "Newell had an audacious goal. He intended to dismantle the U.S.-based gun trafficking network that supplied the formidable Mexican Sinaloa Cartel" led by Joaquin "EL Chapo" Guzman.

The Republican draft report on Operation Fast and Furious says that Newell and four other ATF officials share much of the blame for what went wrong with the Arizona gun-smuggling probe.

All five were removed from their jobs and reassigned a year ago. Attorney General Eric Holder has said further personnel changes could be made, depending on the findings in an upcoming review of Fast and Furious by the Justice Department inspector general.

Schmaler said the report does signal a notable shift in that the Issa-led House Oversight and Government Reform Committee "finally acknowledges what the attorney general and other department officials have been saying from the beginning - that the flaws in this operation, and in previous ones, had their origins in the field in Arizona and occurred, in part, due to weak oversight by ATF leadership."

A second still-unreleased report by Republican congressional investigators on Operation Fast and Furious will deal with the roles of the deputy attorney general's office and the Justice Department's criminal division. A third report will deal with the roles of the attorney general and other top officials at the Justice Department in responding to the controversy after it erupted publicly in early 2011.

The third report will follow what is likely to be a lawsuit against the attorney general by the Republican-controlled House seeking Justice Department documents detailing how Justice officials decided to respond to the congressional investigation.

The House voted June 28 to hold the attorney general in contempt of Congress for withholding material sought by Issa's committee. President Barack Obama invoked executive privilege to order Holder not to turn over the documents on grounds that they reveal internal executive branch advice and recommendations.